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Abstract:

A system and method of increasing data throughput in a wireless
communications network between a base station (BS) and one or more mobile
stations (MS) includes establishing a service flow (SF) and initially
enabling a hybrid automated repeat request (HARQ) protocol; determining,
at a particular time, the measure of quality of the communications
channel; comparing the determined measure of quality with a predetermined
channel quality threshold; and selectively disabling the HARQ protocol
based upon a first comparison result while continuing the SF between the
BS and MS. In other aspects, after selectively disabling the HARQ
protocol, the method further includes determining that the time-varying
measure of quality of the communications channel has deteriorated below
the predetermined channel quality threshold; and selectively re-enabling
the HARQ protocol in the established SF.

Claims:

1.-21. (canceled)

22. A method of increasing data throughput in a wireless communications
network over which a radio frequency (RF) signal is transmitted between a
base station (BS) and a mobile station (MS) over a communications channel
having a time-varying measure of quality, the method comprising: enabling
a hybrid automated repeat request (HARQ) protocol between the BS and the
MS, wherein a service flow (SF) is established between the BS and the MS;
comparing the time-varying measure of quality of the communications
channel with a predetermined channel quality threshold, wherein the
time-varying measure of quality of the communications channel is
determined based upon a statistic of a Physical
Carrier-to-Interference-Ratio (PCINR) reported by the MS; and selectively
disabling the HARQ protocol based upon a comparison result of said
comparing operation while continuing the SF between the BS and MS.

23. The method of claim 22, wherein the statistic comprises a Standard
Deviation (SD) of the PCINR.

24. The method of claim 23, wherein the time-varying measure of quality
of the communications channel is determined further based upon a packet
error rate r determined by the BS, wherein r=NACK/(ACK+NACK).

25. The method of claim 24, wherein the time-varying measure of quality
of the communications channel is determined as a ratio of the SD of the
PCINR and the packet error rate r.

26. The method of claim 22, wherein, after selectively disabling the HARQ
protocol: determining that the time-varying measure of quality of the
communications channel has deteriorated below the predetermined channel
quality threshold; and selectively reenabling the HARQ protocol in the
established SF.

27. The method of claim 26, wherein, after the HARQ protocol is
selectively reenabled, maintaining the HARQ protocol as enabled, based
upon a determination that the time-varying measure of quality of the
communications channel is determined to be greater than an
operator-selectable first threshold value.

28. The method of claim 22, wherein, after the HARQ protocol is
selectively disabled, maintaining the HARQ protocol as disabled, based
upon a determination that the time-varying measure of quality of the
communications channel is determined to be less than an
operator-selectable second threshold value.

29. The method of claim 22, wherein the HARQ protocol is used in a WiMAX
network implemented, at least in part, under the IEEE Standard 802.16.

30. A base station (BS) coupled to one or more subscriber stations (SS)
and/or mobile stations (MS) over a wireless radio access network (RAN),
the base station comprising: a transceiver; a baseband processor coupled
to said transceiver; and a hybrid automatic repeat request (HARQ)
processor coupled to said baseband processor, said HARQ processor
comprising: a channel quality evaluation module, wherein the channel
quality evaluation module is configured to utilize a Standard Deviation
(SD) of a Physical Carrier-to-Interference-Ratio (PCINR) reported by one
of the one or more subscriber stations (SS) and/or mobile stations (MS)
to determine a relative channel quality; and a HARQ enable/disable
controller operatively coupled to said channel quality evaluation module
and configured to selectively enable and/or disable a HARQ protocol
within an established service flow (SF).

32. A non-transitory computer-readable storage medium storing computer
readable code thereon which, when executed by a computer, causes the
computer to carry out operations related to increasing data throughput in
a wireless communications network over which a radio frequency (RF)
signal is transmitted between a base station (BS) and a mobile station
(MS) over a communications channel having a time-varying measure of
quality, the operations comprising: enabling a hybrid automated repeat
request (HARQ) protocol between the BS and the MS, wherein a service flow
(SF) is established between the BS and the MS; comparing the time-varying
measure of quality of the communications channel with a predetermined
channel quality threshold, wherein the time-varying measure of quality of
the communications channel is determined based upon a statistic of a
Physical Carrier-to-Interference-Ratio (PCINR) reported by the MS; and
selectively disabling the HARQ protocol based upon a comparison result of
said comparing operation while continuing the SF between the BS and MS.

33. The computer-readable storage medium of claim 32, wherein the
statistic comprises a Standard Deviation (SD) of the PCINR.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Application is related to co-pending U.S. patent application
Ser. No. ______ (Attorney Docket No. 017421-0379806) entitled "System and
Method for Hybrid Schemes of MIMO Mode Decision" and co-pending U.S.
patent application Ser. No. ______ (Attorney Docket No. 017421-0379807)
entitled "System and Method for Adaptive Control of an Averaging
Parameter", both of which are concurrently filed herewith and both of
which are hereby incorporated by reference herein in their entirety.

BACKGROUND

[0002] In one or more embodiments, this disclosure is directed to a system
and method useful for generating and processing automatic repeat request
(ARQ) signals in wireless communications networks. In particular, this
application is directed to a system and method for dynamic control of ARQ
signals in wireless communications networks that involve a hybrid
approach over conventionally known signal protocols and communications
standards. Even more particularly, this application is directed to a
system and method for improving communication channel performance by the
dynamic control of hybrid ARQ (HARQ) in Broadband Wireless Access (BWA)
communications systems based upon monitoring and selectively responding
to changing communication channel conditions to improve data throughput
and/or the number of users that may access the communications network.

[0003] As a result of the demand for longer-range wireless networking, the
IEEE Standard 802.16 was developed. The IEEE 802.16 standard is often
referred to as Wireless Metropolitan Area Network (WiMAX), "mobile
WiMax", or less commonly as WirelessMAN or the Air Interface Standard.
This standard provides a specification for fixed broadband wireless
metropolitan access networks ("MANs") that use a point-to-multipoint
architecture. Such communications can be implemented, for example, using
orthogonal frequency division multiplexing ("OFDM") communication. OFDM
communication uses a spread spectrum technique distributes the data over
a large number of carriers that are spaced apart at precise frequencies.
This spacing provides the "orthogonality" that prevents the demodulators
from seeing frequencies other than their own. Expected data throughput
for a typical WiMAX network is 45 MBits/sec per channel. The 802.16e
standard defines a media access control ("MAC") layer (OSI level 2,
sometimes referred to as the "Radio Link Control" or "RLC" layer) that
supports multiple physical layer specifications customized for the
frequency band of use and their associated regulations. This MAC layer
uses protocols to ensure that signals sent from different stations using
the same channel do not interfere with each other or "collide".

[0004] The IEEE 802.16 system architecture, for example, consists of two
logical entities, the Base Station (BS) and the Subscriber Station (SS).
Both the BS and SS have instances of the IEEE 802.16 MAC and Physical
Layer 1 (PHY), in addition to other support functions. However, specific
functions performed by the MAC or PHY differ depending on whether it is a
BS or SS, and the IEEE 802.16 standard defines the BS- and SS-specific
behavior in detail. The term SS is applied in a fixed context, while the
MS is used in a mobile environment, as introduced by IEEE Std 802.16e.

[0005] In Point-to-Point (PtP) and Point-to-Multipoint (PMP) networks, the
BS and SS are in a master-slave relationship, where the SS must obey all
medium access rules enforced by the BS. The mobile station (MS) defined
in the IEEE 802.16 mobility extension (IEEE Std 802.16e) requires support
for additional SS-specific functions such as mobility management,
handoff, and power conservation. In this disclosure, the term "SS" is
intended to not only include fixed or relatively immobile terminal
equipment, but to also include MS functionality of mobile user terminal
equipment, unless specifically stated otherwise. One of the basic
differences between the BS and SS in a PMP network configuration is that
the BS, which acts as a centralized controller and a centralized
distribution/aggregation point, has to coordinate transmissions to/from
multiple SSs, whereas the SS need only to deal with one BS. All traffic
originating from an SS, including all SS-to-SS traffic must go through
the BS. Therefore, in a typical IEEE 802.16 system, the BS has to have
additional processing and buffering (i.e., memory) capability in
comparison to a typical SS to support a reasonable number of SSs.

[0006] The functions of the BS and SS depend on the operation mode,
namely, PMP or mesh. The functions of the Base Station include:

[0018] Various methods and metrics have been developed to indicate the
channel condition or Channel Quality Indicator (CQI). Exemplary metrics
include a Physical Carrier to Interference plus Noise Ratio (PCINR), a
Received Signal Strength Indicator (RSSI), an ACK/NACK ratio that
indicates a proportion of successful data transmissions to unsuccessful
transmission (thereby indicating channel stability), PCINR Standard
Deviation (SD) that may indicate Doppler and fading effects that result
from movement of the MS, and other indicators. These indicators may be
generated at the MS or SS and transmitted to the BS by known techniques
of representing the CQI. The BS may receive the channel condition
indicators, e.g., CQI, and attempt to adjust communication in response to
changes to the channel condition. For example, the BS may perform
download link adaption such as, for example, selecting an appropriate
Modulation Coding Scheme (MCS) according to the channel condition in
response to various changes to the channel condition. Knowing current and
accurate channel condition information may enhance the ability of the BS
to respond to changes to the channel condition. Current systems, however,
are not configured to make use of such channel condition information to
change various signaling parameters, particularly in an automated
fashion.

[0019] Manual selective implementation of a well-known error control
technique for data transmission, Automatic repeat-request (ARQ), utilizes
acknowledgments and timeouts to achieve reliable data transmission. ARQ
acknowledgments are messages sent by the receiver to the transmitter to
indicate that the receiver correctly received an information unit.
Timeouts are reasonable points in time after the sender transmits the
information unit. The sender usually re-transmits the information unit if
it does not receive an acknowledgment before the timeout. It continues to
re-transmit the information unit until it either receives an
acknowledgment from the receiver or exceeds a predefined number of
re-transmission attempts. FIG. 2 depicts a notional timeline and message
flow for packet transmission/acknowledgement and retransmission in cases
where no acknowledgement (negative acknowledgement or NACK) of a
transmitted packet is received.

[0021] Conventional Hybrid ARQ (HARQ) is a commonly used extension of the
ARQ error control method that exhibits better performance, particularly
over wireless channels, but at the cost of increased implementation
complexity. HARQ is used in several conventional wireless communications
systems including High-Speed Downlink Packet Access (HSDPA) and
High-Speed Uplink Packet Access (HSUPA) (i.e., third generation mobile
telephony communications protocols in the High-Speed Packet Access (HSPA)
family) which allow networks based on Universal Mobile Telecommunications
System (UMTS) to have higher data transfer speeds and capacity on
downlink and uplink, respectively, for mobile phone networks using the
UMTS.

[0022] HARQ has also been used in the currently implemented IEEE
802.16-2005 standard for mobile broadband wireless access, i.e., "mobile
WiMAX". Presently, HARQ provides an important technology for increasing
data transmission reliability and data throughput in mobile communication
systems. Specifically, in the WiMax implementation, HARQ refers to a
combination of ARQ and PHY layer reception techniques like Forward Error
Correction (FEC) and signal combining techniques. Different from ARQ
operating solely at the MAC layer, HARQ allows the receiver to perform
soft-combining of retransmitted packets and therefore may provide some
measure of improvement in spectral efficiency. There are two well-known
HARQ techniques: the first known as Incremental Redundancy (IR) and the
second known as chase combining, discussed further below.

[0023] HARQ is an important technique for link adaptation, and makes
aggressive modulation and coding schemes (MCS) decisions possible, e.g.,
the use of OFDM. Thus, the use of HARQ can result in considerable
increased data throughput, and/or can enable more users to access the
network. In HARQ, the transmitter and the receiver cooperate on an
information unit (HARQ sub burst, burst, packet or block) level. The
receiver is capable of indicating successful (via ACKs) or unsuccessful
(via NACKs) reception of the last transmitted information unit or block.
The transmitter comprises several parallel HARQ sub processors (e.g., in
802.16e referred to as HARQ sub-channels), each of which performs
operations of transmitting user information units, receiving ACK/NACK
information or other ACK indications in response, and performing either a
retransmission when needed or transmitting the next information units.
The ACK indication may be direct whereby a specific ACK or NACK
indication is sent. In HARQ, the receiver takes advantage of any previous
retransmissions by decoding the information unit or block based on
information gathered from all the retransmissions of the same information
unit or block, thus improving overall performance of the communications
link.

[0024] In IEEE 802.16e, HARQ schemes are optional parts of the MAC layer,
and can currently only be enabled on a per-terminal per connection basis,
when a Service Flow (SF) is established between the BS and SS. The
per-terminal HARQ and associated parameters are specified and negotiated
during the initialization procedure, and currently cannot be altered for
an established SF. In other words, once HARQ is enabled, it may not be
changed during the duration of the particular SF.

[0025] As mentioned above, Chase Combining is used in the current WiMAX
profile, although IEEE 802.16e also supports IR. A SS may support IR,
while a MS may support either Chase Combining or IR. For IR, the PHY
layer will encode the HARQ packet generating several versions of encoded
subpackets. Each subpacket is uniquely identified using a subpacket
identifier (SPID). For Chase Combining, the PHY layer encodes the HARQ
packet generating only one version of the encoded packet. As a result, no
SPID is required for Chase Combining HARQ Chase Combining requires all
retransmissions to send the exact same information and to use the
original modulation-coding scheme (i.e. waveform). Note that HARQ
retransmissions are asynchronous, in the sense that all HARQ bursts
undergo opportunistic scheduling. The maximum number of retransmissions
is determined by target residual Packet Error Rate (PER). Typically the
number of HARQ retransmissions is set to four, for a PER of
1×10-4 (this is the case for IR as well).

[0026] A benefit of employing HARQ is that it can be used to mitigate the
effects of channel and interference fluctuation. HARQ provides an
improvement in performance due to the SNR improvement derived from the
energy and time diversity gain achieved by (1) combining retransmitted
packets with previous erroneously decoded packets and/or (2) using
Incremental Redundancy (IR) to realize additional coding gain.

[0027] Using WiMAX as an example, a resource region for HARQ ACK channels
is allocated using the HARQ ACK region allocation Information Element
(IE). This resource region may include one or more ACK channels for HARQ
support-enabled MSs, e.g., ACKCH 150n in FIG. 1. The uplink (UL) ACK
channel occupies half a slot in the HARQ ACK channel region, which may
override the fast feedback region. This UL ACK channel is assigned
implicitly to each HARQ-enabled burst, according to the order of the
HARQ-enabled downlink (DL) bursts in the DL-MAP. Thus, using this UL ACK
channel, SSs or MSs can quickly transmit ACK or NACK feedback for DL
HARQ-enabled packet data.

[0028] HARQ may also divide into several types. In the simplest version of
HARQ types, called Type I HARQ, both Error Detection (ED) and Forward
Error Correction (FEC) information to each message prior to transmission.
When the coded data block is received, the receiver first decodes the
error-correction code. If the channel quality is sufficient, all
transmission errors should be correctable, and the receiver can obtain
the correct data block. If the channel quality is bad and not all
transmission errors can be corrected, the receiver detects this situation
using the error-detection code, the received coded data block is
discarded, and the receiver requests retransmission. The more
retransmissions that are required for successful reception, the less are
the available resources (e.g., transmission power, number of available
transmission slots) to provide data throughput for other users.

[0029] In the more sophisticated Type II HARQ, only (1) ED bits or (2) FEC
information and ED bits are sent on a given transmission, typically
alternating on successive transmissions. It is important to note that
detection typically adds only a few bytes to a message, resulting in a
relatively small incremental increase in message length. FEC, however,
adds error correction parities, which often double or triple the message
length. In terms of throughput, standard ARQ typically expends a few
percent of channel capacity for reliable protection against error, while
FEC ordinarily expends half or more of all channel capacity for channel
improvement.

[0030] In Type II HARQ, the first transmission contains only data and
error detection. If it is received in error, the second transmission
includes FEC parities and error detection information. If the second
transmission is received in error, error correction is attempted by
combining the information received from both transmissions. Incorrectly
received coded data blocks are often stored in buffer memory at the
receiver rather than discarded. When the retransmitted block is received,
the two blocks are combined, using a technique known as Chase Combining,
which increases the likelihood of correctly decoding the message.

[0031]FIG. 1 depicts the architecture of a WiMAX network implemented in
accordance with various aspects of IEEE Standard 802.16. In FIG. 1, base
station (BS) 110 may communicate with one or more Mobile
Stations/Subscriber Stations (MS/SS) 130a-130n over network 120 via an
associated communication channel 140a-140n. In this disclosure, the terms
"SS" and "MS" are used interchangeably, although it is recognized that MS
implies the use of mobility enhancements. MS/SS 130a-130n may be
relatively fixed or immobile terminal equipment, or may be equipment that
includes the mobility functions of a MS, e.g., a cell phone or laptop
computer traveling in an automobile or airplane. Various factors such as
the existence of ambient interference around the SS or BS, movement of
the SS, and other factors may degrade or otherwise alter the channel
condition of the communication channel, making the use of HARQ desirable
to ensure reliable communications over channels 140a-140n. HARQ uplink
Acknowledgement Channels (ACKCH) 150a-150n allow each MS/SS 130a-130n to
acknowledge packet receipt to the BS by use of a HARQ signal transmission
over a dedicated HARQ ACK channel. Although HARQ provides advantages
under some channel conditions, these ACKCH channels represent additional
channel overhead that will decrease data throughput when channel
conditions are such that communication may be reliably maintained without
HARQ being used. Channel Quality Indicator (CQI) channels 160a-160n
provide a path for the MS or SS to identify the relative quality of the
communication channel to BS 110 using known techniques.

[0032]FIG. 2 depicts an example of conventional ARQ operation in which
each packet is a MAC layer packet containing one or more ARQ blocks. MAC
layer ARQ alone does not improve spectral efficiency. However, with its
retransmission mechanism to correct packet errors at the cost of extra
delays, ARQ provides a more reliable link layer as seen by applications,
and permits link adaptation for higher spectral efficiency. As can be
seen in FIG. 2, there may be some inefficiency when an ACK is lost due to
error, and a correctly received packet is retransmitted.

[0033] Chase Combining HARQ in the PHY layer is supported to further
improve the reliability of a retransmission stored in a HARQ buffer by
combining one or more previous transmissions decoded in error. In HARQ
Chase Combining, all retransmissions sent include the same information
and use the original modulation-coding scheme (MCS). To streamline the
HARQ feedback, a dedicated ACK channel is also provided on the
transmission side for purposes of HARQ ACK/NACK signaling, e.g. ACKCH
channels 150a-150n in FIG. 1.

[0034] In the case of WiMax (or other communication methodologies), the
system may, from time to time, encounter communication channel conditions
that result in or near complete packet reception, making the use of HARQ
or other signaling protocols unnecessary, at least for a portion of the
time the communication channel is in use for a particular SF. In this
situation, the overhead associated with HARQ signaling (e.g., ACKCH
150a-150n in FIG. 1) must still be allocated because, in conventional
systems known to date that implement a HARQ signaling scheme, e.g.,
WiMax, HARQ may only be enabled at the time a SF is established between a
BS and SS, and there is no method or system that solves the problem of
the increased overhead and decreased data throughput when HARQ may not be
necessary for reliable communications.

[0035] Under the current WiMax standard, HARQ and associated parameters
are specified and negotiated using Station Basic
Capability-Request/Response (SBCREQ/RSP) messages during network entry or
re-entry procedure. Under the Standard, a MS shall support per-connection
based HARQ, and HARQ can be enabled on a per Connection ID (CID) basis by
using Dynamic Service Addition/Dynamic Service Change (DSA/DSC) messages.

[0036] HARQ may be enabled or disabled by setting the "ACK disable" bit.
HARQ is enabled if "ACK disable"=0, and is disabled otherwise, i.e. "ACK
disable"=1. The DL HARQ sub-burst Information Element (IE) defines the
"ACK disable" bit setting. However, it may be difficult to determine
whether HARQ should be enabled or disabled during initial channel setup,
and HARQ may not continue to be necessary if the communication channel's
quality improves to an acceptable or desirable level.

[0037] A further problem with the current standards-based WiMAX
implementation is that the HARQ Enable/Disable decision is fixed and
static. The decision on HARQ Enable/Disable is made only when a Service
Flow (SF) is setup. Once HARQ is enabled or disabled at the time the SF
is established, the communication channel continues with the same HARQ
configuration, i.e., no change during SF, regardless of the relative
channel condition. Thus, even when channel quality is sufficient for a
particular QoS requirement without HARQ, HARQ will continue to be used,
resulting in increased network overhead.

[0038] Thus, even though conventional HARQ often serves useful purposes,
there is a need for a system and method that are capable of enabling
network elements in a communication link to dynamically select HARQ
processing after a SF has been established to account for the
availability of a good communication channel for which HARQ is not
required at all times.

[0039] Further, the currently-implemented WiMAX implementation has
difficulty in making a decision whether HARQ should be enabled or
disabled when a new SF is setup since there generally is not enough
information about the channel condition for a new SF. Currently, WiMAX
always configures HARQ to be enabled in order to minimize the risk of low
throughput on the downlink (DL) with the cost of a UL resource for ACKCH.
Moreover, the number of Acknowledgement Channels must be increased with
the number of users that are enabling HARQ, leading to decreased
efficiency in terms of bandwidth utilization and increased overhead.

[0040] While the current 802.16 WiMAX standard states that ACK disable bit
is configurable to be either a "1" or "0", the current implementation of
the standard provides no guidance concerning when and under what
circumstances the ACK disable bit should be set to either a "1" or "0".
As it currently is implemented, any mechanism may be applied, which
results in various implementation issues for a large number of
stakeholders seeking to widely implement WiMAX.

[0041] What is needed for improved channel utilization and increased
efficiency in WiMAX networks is a dynamically selectable HARQ
Enable/Disable scheme that uses information on changing channel
conditions to determine whether HARQ should continue to be enabled or
disabled during an ongoing SF by selectively being able to set the "ACK
disable" bit.

SUMMARY

[0042] The system and method of this disclosure provide various features,
functions, and capabilities as discussed more fully in the detailed
description, and as summarized below. For example, this disclosure
provides a novel and useful signaling method and system for use in a
communications link, with particular application in wireless
telecommunication systems such as those adhering to IEEE 802.16 (WiMAX),
3GPP, 3GPP2, etc. communication standard specifications that utilize HARQ
protocol mechanisms, but is not limited to use with these systems.

[0043] One major challenge in broadband wireless access networks is to
provide fast, reliable services to time-sensitive communications.
Embodiments of this disclosure provide a dynamic HARQ scheme for wireless
communications systems which follows the multi-channel chase combining
HARQ adopted by WiMAX, for example, while enabling the base station (BS)
to proactively react to poor channel conditions by selectively
implementing HARQ on a per burst or frame basis.

[0044] Various embodiments of this disclosure dynamically implement HARQ
by enabling the BS to selectively enable or disable the use of HARQ after
a SF has been established, thus reducing overhead and increasing data
throughput and/or the number of users that may access the communications
network.

[0045] In one or more embodiments, a Dynamic Enable/Disable system and
method are disclosed where HARQ is selectively Enabled or Disabled by an
"ACK disable" bit during a SF depending on channel condition. In this
disclosure, "dynamic" means that HARQ is configurable to be enabled or
disabled on a "per burst" or per frame basis, which does not necessarily
mean a "real time" change.

[0046] Various metrics may be used in making the initial and subsequent
decisions as to whether to enable or disable HARQ. For example, Standard
Deviation (SD) of PCINR, or error rate r=NACK/(ACK+NACK) may be used
either alone or in combination to aid in making a threshold decision on
HARQ enablement.

[0047] In one embodiment, a method of increasing data throughput in a
wireless communications network over which a radio frequency (RF) signal
is transmitted between a base station (BS) and one or more subscriber
stations (SS) and/or mobile stations (MS) over a communications channel
having a time-varying measure of quality includes establishing a service
flow (SF) and initially enabling a hybrid automated repeat request (HARQ)
protocol between the BS and the MS; determining, at a particular time,
the measure of quality of the communications channel; comparing the
determined measure of quality with a predetermined channel quality
threshold; and selectively disabling the HARQ protocol based upon a first
comparison result while continuing the SF between the BS and MS. In one
aspect of this embodiment, the method further includes determining, at a
subsequent time, that the time-varying measure of quality of the
communications channel has deteriorated below the predetermined channel
quality threshold; and selectively reenabling the HARQ protocol in the
established SF.

[0048] In another embodiment, a base station (BS) coupled to one or more
subscriber stations (SS) and/or mobile stations (MS) over a wireless
radio access network (RAN) includes a transceiver; a baseband processor
coupled to said transceiver; a hybrid automatic repeat request (HARQ)
processor coupled to said baseband processor and which includes an
ACK/NACK processing module; a channel quality evaluation module; a HARQ
enable/disable controller operatively coupled to said ACK/NACK processing
module and said channel quality evaluation module and operative to
selectively enable and/or disable a HARQ protocol within an established
service flow (SF). In one aspect of this embodiment, if the HARQ protocol
is enabled, the HARQ enable/disable controller is configured to compute a
metric m comprising a ratio of a Standard Deviation (SD) of a Physical
Carrier-to-Interference-Ratio (PCINR) reported by one of the one or more
subscriber stations (SS) and/or mobile stations (MS) to a packet error
rate r determined by the BS, wherein the metric m=SD/r, and
r=NACK/(ACK+NACK); and responsive to a first comparison result between
the computed metric m and an operator-selectable first threshold value,
the HARQ enable/disable controller is further configured to selectively
disable the HARQ protocol within the established service flow (SF). In a
further aspect of this embodiment, if the HARQ protocol is disabled, the
HARQ enable/disable controller is configured to compare the SD to an
operator-selectable second threshold value and determine a second
comparison result; and selectively reenable the HARQ protocol within the
established service flow (SF) in response to the second comparison
result.

[0049] In another embodiment, a computer-readable medium includes computer
readable code embodied therein which, when executed by a computer, causes
the computer to carry out the functions of establishing a service flow
(SF) and initially enabling a hybrid automated repeat request (HARQ)
protocol between the BS and the MS; determining, at a particular time,
the measure of quality of the communications channel; comparing the
determined measure of quality with a predetermined channel quality
threshold; selectively disabling the HARQ protocol based upon a first
comparison result while continuing the SF between the BS and MS; after
selectively disabling the HARQ protocol, determining, at a subsequent
time, that the time-varying measure of quality of the communications
channel has deteriorated below the predetermined channel quality
threshold; and selectively reenabling the HARQ protocol in the
established SF.

BRIEF DISCUSSION OF THE DRAWINGS

[0050]FIG. 1 provides a block diagram of a conventional wireless
communication system in which the system and method of this disclosure
may be implemented;

[0058] FIG. 8 provides a functional block diagram of a Base Station
illustrating a HARQ processing module of an embodiment.

DETAILED DESCRIPTION

[0059] In the discussion of various embodiments and aspects of the system
and method of this disclosure, examples of MS/SS 130 may include any one
or more of, for instance, a personal computer, portable computer,
personal digital assistant (PDA), workstation, web-enabled mobile phone,
WAP device, web-to-voice device, or other device. Those with skill in the
art will appreciate that the inventive concept described herein may work
with various system configurations.

[0060] In addition, various embodiments of this disclosure may be made in
hardware, firmware, software, or any suitable combination thereof.
Aspects of this disclosure may also be implemented as instructions stored
on a machine-readable medium, which may be read and executed by one or
more processors. A machine-readable medium may include any mechanism for
storing or transmitting information in a form readable by a machine
(e.g., a computing device). For example, a machine-readable storage
medium may include read only memory, random access memory, magnetic disk
storage media, optical storage media, flash memory devices, and others.
Further, firmware, software, routines, or instructions may be described
herein in terms of specific exemplary embodiments that may perform
certain actions. However, it will be apparent that such descriptions are
merely for convenience and that such actions in fact result from
computing devices, processors, controllers, or other devices executing
the firmware, software, routines, or instructions.

[0061] According to various embodiments, CQI Channels 160a-160n in FIG. 1
may include a Standard Deviation of the channel condition information
described above. In other words, MS/SS 130n may report a Standard
Deviation of channel condition information. Standard Deviation of the
channel condition information may indicate the combined effect of Doppler
and fading. For example, a higher PCINR Standard Deviation over a number
of time points may indicate high Doppler and fast fading effects on the
communication channel throughout the number of time points as compared to
a lower PCINR Standard Deviation. Each time point may represent a
transmission of a communication between BS 110 and MS/SS 130 on a
communication channel. A lower PCINR Standard Deviation may indicate low
Doppler and low fading effects throughout the number of time points as
compared to a higher PCINR Standard Deviation. Thus, the PCINR Standard
Deviation, for example, may be used to indicate channel condition of the
communication channel throughout the number of time points. The number of
time points observed by the MS/SS 130 in order to generate the Standard
Deviation may be configurable. In other words, a vendor implementing the
system or method may vary the number of time points used to generate the
Standard Deviation. For example, the number of time points may include
all or a portion of the number of time points since communication on a
communication channel is established between BS 110 and MS/SS 130n.

[0062]FIG. 3A is a two-dimensional graph illustrating an example of PCINR
data 308a over time 304 exhibiting relatively high Standard Deviation
about a mathematical mean PCINR 306a, according to an embodiment. PCINR
values 302 are shown as a function of time 304. It should be understood
that in FIG. 3A and any other figures illustrating a two-dimensional
graph herein, the graphs are illustrative only and should not be viewed
as limiting. For example, the axes may be reversed as appropriate without
departing from the scope of this disclosure. As previously noted, a
higher Standard Deviation of PCINR, for example, over a number of time
points may indicate high Doppler and fast fading effects of the
communication channel as compared to a lower Standard Deviation.

[0063]FIG. 3B is a two-dimensional graph illustrating an example of PCINR
data 308b over time 304 exhibiting relatively low PCINR Standard
Deviation about a mathematical mean PCINR 306b, according to an
embodiment. PCINR values 302 are shown as a function of time 304. As
previously noted, a lower PCINR Standard Deviation, for example, over a
number time points may indicate low Doppler and slow fading effects of
the communication channel as compared to a higher PCINR Standard
Deviation.

[0064] BS 110 may be configured to use the PCINR information from CQI
Channels 160n to perform downlink adaption for a subsequent communication
with MS/SS 130n. In particular, if HARQ is not enabled, BS 110 may
selectively enable HARQ according to the Standard Deviation of PCINR
reported by a particular MS/SS 130. Thus, channel condition information
based on CQI or PCINR data may enhance the ability of BS 110 to select a
more appropriate signaling scheme (i.e., to either selectively and
dynamically enable or disable HARQ) for communications to reflect
changing channel conditions as compared to a static implementation of
HARQ-enabled or disabled.

[0065] According to various embodiments, HARQ ACKCH channels 150n may
include another type of channel stability information, such as, for
example, an ACK/NACK ratio. The ACK/NACK ratio indicates a ratio of
successful transmissions and non-successful transmissions, thereby
indicating channel stability.

[0066] ACK/NACK feedback information provides useful information
representing a channel condition and HARQ performance. During a certain
time window, if most feedbacks are ACKs, then that implies that channel
is good or HARQ is working very well in unstable channel condition. The
error rate r is defined by r=NACK/(ACK+NACK). If r is relatively high, it
implies that the channel is not good (e.g., unstable) or that HARQ, if
enabled, is not working well. If r is relatively low, it implies that the
channel is good or that HARQ is working very well with the unstable
channel condition.

[0067] Although both SD PCINR and error rate r provide useful information,
synergy may be achieved by the use of these two parameters in combination
as a measure of channel stability. In one or more embodiments, a metric m
combining SD PCINR with ACK/NACK feedback, i.e., r, is defined as:

m=SD/r,

where SD is the Standard Deviation of PCINR and

r=NACK/(ACK+NACK).

[0068] If SD is relatively high and error rate r is relatively low such
that the metric m is a relatively large number, the channel is unstable
and the error rate is low. In this situation, better overall system
performance would be obtained by keeping HARQ enabled. However, if SD is
low and the error rate r is high such that the metric m is small, the
channel is stable and the error rate is high, better system performance
would result by keeping HARQ disabled. Exemplary values for SD and r may
be SD=6.3 (i.e., 8 dB), and r=10%, such that m=6.3/0.1=63. Other values
for SD and r may be appropriate for different network requirements and
conditions, as would be known to a person with ordinary skill in the art.

[0069] In various embodiments, HARQ is selectively and dynamically enabled
or disabled based on feedback information from MS/SS 130, i.e., SD of
PCINR alone (if HARQ is disabled) and in combination with packet error
rate r=NACK/(ACK+NACK) (if HARQ is enabled), during a SF. HARQ enable
(ON) and disable (OFF) are dynamically configured. HARQ ON/OFF states and
their transitions are depicted in FIG. 4.

[0070] In FIG. 4, for the state where HARQ is "OFF", and if the channel is
stable, then no gain from HARQ would be expected. A stable channel
implies that the SD of PCINR is low or that the PCINR is increased. When
the channel becomes unstable, then a processing gain from enabling HARQ
would be expected. This implies that SD of PCINR is high, i.e., PCINR has
high variability due to doppler or fading, for example, or that PCINR has
decreased.

[0071] For the state in FIG. 4 where HARQ is "ON", a stable channel
condition could also imply that the number of packet errors represented
by the number of NACKs is low. An unstable channel condition implies that
the number of packet errors represented by the number of NACKs is high.
Standard Deviation of PCINR may represent channel fluctuation. If the
Standard Deviation is relatively high, it implies that a channel is more
fluctuating. If the Standard Deviation is low, it implies that a channel
is relatively stable. In a relatively high fluctuating channel
environment, HARQ could be more beneficial to achieve the target burst
error rate (1%) with lower CINR than required at the target error rate
(1%), i.e., a high gain from the use of HARQ could be expected. In a
relatively stable channel environment, HARQ gain may not be achieved or
expected as much in the case of an unstable channel condition.

[0072] Based on the rationale above, the state diagram of FIG. 5 can be
defined, where TH1 and TH2 are operator-selectable/configurable
thresholds for metric m and SD, respectively. If HARQ is enabled, and if
metric m>TH1, then HARQ should remain enabled. If, however, metric
m<TH1, then HARQ should be turned off. Once HARQ is disabled, there
are no "ACKS" or "NACKS" to determine the error rate r. Consequently, SD
PCINR may be used to assess the channel stability/quality. If SD<TH2,
or if the CQI has increased, then HARQ should remain disabled. However,
if SD>TH2, or if CQI is decreased, then the state should transition to
HARQ enabled. By applying the decision rules, the communications network
can improve throughput and capacity. It should be noted that the state
transition diagrams in FIGS. 4 and 5 are occurring during a previously
established SF, contrary to conventional approaches which use HARQ in a
static and unchanging mode.

[0073] A flowchart of a method of an embodiment is provided in FIG. 6.
Process 600 starts at step 610, in which a service flow (SF) is
established between the BS and a MS, for example. A HARQ signaling
protocol is enabled at step 620. Thereafter, channel stability is
determined at step 630 by one or more techniques, as discussed above,
e.g., SD PCINR, error rate r, CQI, or metric m. A comparison is made
between the current measure of channel stability and an
operator-selectable threshold at step 640. If the channel is assessed as
being stable, then the HARQ protocol is disabled at step 650, and the
process returns to step 630 to re-determine channel stability. If,
however, the channel is assessed as being unstable at step 640, then the
process moves to re-enable HARQ signaling at step 660, after which the
process returns to step 630 to re-determine channel stability.

[0074] A flowchart of a method of an embodiment is provided in FIG. 7.
Process 700 starts at step 710, in which a service flow (SF) is
established between the BS and a MS, for example. A HARQ signaling
protocol is enabled at step 720. Since HARQ is now enabled, ACKs and
NACKs may be received in addition to channel quality information, which
may be in the form of SD of PCINR. A stability metric m=SD/r is
determined at step 730, and the resultant metric m is compared to a first
operator-selectable threshold value TH1 at step 740. If m>TH1, then
the process continues by returning to step 730 to re-determine the
stability metric, m. If, however, m<TH1, then HARQ is disabled at step
750. Since HARQ is disabled, ACKs and NACKs are no longer available to
assess communications channel quality. So now, SD PCINR or CQI may be
used at step 760 for comparison to a second operator-selectable threshold
TH2. If SD<TH2, then the process returns to step 750 with HARQ
remaining disabled until SD>TH2, after which the process returns to
enable HARQ at step 720.

[0075] In the embodiment of FIG. 8, a base station base station (BS) is
communicatively coupled to one or more subscriber stations (SS) and/or
mobile stations (MS) over a wireless radio access network (RAN). The base
station includes transceiver 810 coupled to baseband processor 820. HARQ
processor 830 is coupled to baseband processor 820. HARQ processor 820
includes ACK/NACK processing module 831 that is configured to receive and
process ACKs and/or NACKs, and to determine a packet error rate, for
example. A channel quality evaluation module, e.g., SD PCINR/CQI
evaluation module 833 is configured to evaluate indications of channel
quality transmitted over CQI channels 160n. HARQ enable/disable
controller 835 is operatively coupled to ACK/NACK processing module 831
and channel quality evaluation module 833, and operates to selectively
enable and/or disable a HARQ protocol within an established service flow
(SF) depending on evaluation of SD PCINR and/or packet error rate. Memory
837 may be available to one or more of the above modules for storing
data, including any operator-selectable threshold values.

[0076] SD PCINR/CQI evaluation module 833 may be configured to utilize SD
PCINR that represents communications channel fluctuation reported by one
of the one or more SS and/or MS to determine a relative channel quality,
or SD PCINR/CQI evaluation module 833 may utilize a channel quality
indication (CQI) reported by one of the one or more SS and/or MS.

[0077] ACK/NACK processing module 831 may be configured to determine a
packet error rate r, wherein r=NACK/(ACK+NACK). Further, if the HARQ
protocol is enabled, HARQ enable/disable controller 835 may be configured
to compute the metric m described above. Further, responsive to a first
comparison result between the computed metric m and an
operator-selectable first threshold value, HARQ enable/disable controller
835 may be further configured to selectively disable the HARQ protocol
within the established SF.

[0078] If the HARQ protocol is disabled, the HARQ enable/disable
controller 835 may be configured to compare the SD to an
operator-selectable second threshold value and to determine a second
comparison result and, depending on the second comparison result, HARQ
enable/disable controller 835 may selectively reenable the HARQ protocol
within the established SF. In addition, the first and second
operator-selectable threshold values may be determined and selected based
upon a desired quality of service (QoS) for the established SF in the
wireless radio access network.

[0079] In addition, base station 800 may also include a computer interface
configured to allow a user to monitor system parameters and to input
selected threshold values into a memory associated with the HARQ
processor.

[0080] The various modules and interfaces described above can be
implemented by any number of processors, memory, and input/output
devices, as are known in the art.

[0081] Various embodiments herein are described as including a particular
feature, structure, or characteristic, but every aspect or embodiment may
not necessarily include the particular feature, structure, or
characteristic. Further, when a particular feature, structure, or
characteristic is described in connection with an embodiment, it will be
understood that such feature, structure, or characteristic may be
included in connection with other embodiments, whether or not explicitly
described. Thus, various changes and modifications may be made to this
disclosure without departing from the scope or spirit of the inventive
concept described herein. As such, the specification and drawings should
be regarded as examples only, and the scope of the inventive concept to
be determined solely by the appended claims.